Amazon had quite a while variety of "graphic novels" or trade paperbacks. Some of older ones or ones non-major publishers take a little bit of time to arrive but it's not a majory problem.
Thankfully I've got a large local comic shop where I live as well as a Forbiden Planet (who I find don't have a massive range of comics and over charge). I still by the monthly releases but only of a few titles, most of the time I'll stick with the trades.
I'd personally suggest Marvel's Runaways and Powers as two atypical superhero themed comics.
There are quite a few Star Wars releated comics if you like you Space Opera that's normally a good place to start.